Fuse switch



July 14, 1936. c. A. FOX 2,047,365

FUSE SWITCH Filed May 20, 1935 2 Sheets-Sheet l ATTOBN'Y July 14, 1936.

LEW.

Filed May 20, 1935 C. A. FOX

FUSE SWITCH 2 Sheets-Sheet 2 Wis) huavrae OMB; 5 Afl/h' fax ATTORNEYPatented July 14, 1936 UNITED STATES PATEN'T. OFFICE FUSE swrrcn CharlesAdin Fox, St. Louis, Mo., assignor to James R. Kearney Corporation, St.Louis, Mo., a corporation of Missouri Application May 20, 1935, SerialNo. 22,408

.17 Claims. (01. 200-122) This invention relates generally to fuseswitches, and more specifically to an improved fuse switch which, inaddition to affording protection against short circuit faults in anelectrical circuit with which the fuse switch is associated, servesalso, because of certain thermal means forming a part of the fuseswitch, to afford maximum protection against overload faults in thecircuit, the predominant object of the invention being to provide animproved fuse switch of this type which is capable of performing itsintended function in a highly efllcient manner.

It is quite generally known to persons familiar with such matters thatfor a number of years it has been the practice to protect distributiontransformers of electrical systems through the use of fuse switches ofvarious types. These fuse switches generally depend on opening thecircuit by melting portions of the fuse elements, or by melting solderedjoints which hold parts of the fuse elements together. The melting ofthe fuse elements or the joints thereof takes place at certainpredetermined current values and is dependent on the size and length ofthe fuse elements, the kind of wire thereof, and the melting point ofthe wire constituting the fuse elements or the solder thereof. Owing tothe fact that a fuse element is necessarily small, the temperature riseof the element follows very closely the current rise in the circuit. Thelag of the temperature curve of the fuse element behind the currentcurve of the circuit can be varied to some extent by changing thephysical dimensions of the material, but essentially the.fuse remains aquick operating unit.

This characteristic makes the fuse ideal for short circuit protection(high current value faults), but naturally prevents it from having thenecessary characteristics for overload protection. In order to preventneedless service interruptions from temporary overloads it is necessary,and has become general practice, to use a fuse element from two to fivetimes the actual capacity of the transformer. With the natural increasein the use of electric service and the ever increasing number ofelectrical devices used, the load on the normal transformer is slowlycreeping upward until finally the original excess capacity will havebeen exceeded, and unless there has been considerable time spent in loadchecking or considerable outlay put in excess transformer capacity, orboth, transformer loss is inevitable.

The improved device disclosed herein, which may be described as athermo-relay fuse switch, comprises a cartridge mechanism which may beinserted in a standard switch mounting. It preserves the high qualityshort circuit protection of the fuse now in general use, and adds tothis the ability to afford overload protection which the present fusedoes not do. This combination 5 enables the excess transformer capacityto be reduced to a minimum, and also provides for the reduction to theminimum of the load survey cost.

Briefly stated, overload protection in the im- 10 proved device isobtained by arranging a small heating element in series with the fuseelement and. interposing heat-insulating material between the heatingelement and a thermo-tripping element. The temperature of thethermo-trip- 15 ping element can be made to lag behind the current flowin the heating element suiiiciently long to care for all temporary loaddemands without interrupting the circuit by having the excess heatabsorbed by adjacent parts of the switch struc- 20 ture, thus keepingthe temperature of the thermo tripping element below the tripping point.In the event, however, of the overload proving permanent, thetemperature of the thermo-tripping element will continue to rise untilthe switch is 5 tripped out, thus protecting the transformer from injurycaused by continued overload. The lag of the temperature of thethermo-tripping element behind the load current is controlled by theamount and character of the heat-insulating meso dium between theheating element and the thermo element, and somewhat by the constructionof the assembly.

Fig. 1 is a side elevation of the improved fuse switch, parts of theswitch mounting being broken 35 away to conserve space. j

Fig. 2 is an enlarged section on line 2-2 of Fig. 1, witha part of thehousing of the heating element broken away in order to show inner partsthereof.

Fig. 3 is a front elevation of the cartridge of the improved fuseswitch.

Fig. 4 is an enlarged, fragmentary view, partly in vertical section andpartly in elevation, of the lower portion of the cartridge of theimproved structure.

Fig. 5 is a vertical section on line 55 of Fig. 4.

Fig. 6 is a fragmentary, inverted, plan view of the cartridge asillustrated in Fig. 4.

Fig. 7 is a fragmentary, side elevation of the lower portion of thecartridge showing said portion as it appears when the theme-trippingelement has been actuated and dropping-out movement of the cartridge hasstarted. 55

In the drawings, wherein is shown for the purpose of illustration,merely, one embodiment of the invention, A designates a standard switchmounting which includes an insulator B, upper and lower line terminals Cand D secured to said insulator, upper and lower contact members E andF, and a bracket G by which the switch mounting is secured to across-arm or other element (not shown) by which it is supported. For thepurpose of this disclosure, the upper contact member E may be consideredto comprise a length of heavy wire fixed to the upper terminal and bentto provide a pair of substantially parallel, forwardly extended legportions between which a portion of the cartridge of the improvedstructure is interposed for the purpose of providing mechanical andelectrical connection between the cartridge and said upper contactmember. The lower contact member F may be considered to comprise aforwardly extended member fixed to the lower terminal D and providedwith laterally extended elements H which serve as hinge members for thecartridge of the improved structure.

Referring now to the cartridge of the improved fuse switch, I designatesan expulsion tube formed of suitable insulating material or combinationsof insulating materials. At its upper end the tube I is provided with acap 2, which is in the form of a sleeve that embraces the upper endportion of the tube, said cap being pinned or otherwise secured to thetube and being provided with an upstanding finger 3 which is interposedbetween and is frictionally gripped by the outwardly extended, parallellegs of the upper contact member E when the cartridge is in the fusingposition, for the purpose of mechanically and electrically connectingthe upper end of the cartridge to the upper contact member E. At the topof the cap 2 an opening is provided which receives a head element 4associated with a fuse element 5, said head element being seated againsta face which surrounds the opening at the top of the cap 2 and having aportion 4' which extends a short distance downwardly into the tube I.The fuse element is attached to the head element 3 and is extendeddownwardly therefrom through the tube I in the usual manner. Also, thecap 2 is provided with a ring 6 which facilitates manual movement of thecartridge into and out of the fusing position with the aid of aninsulated switch stick or fuse puller.

Fixed to the tube I of the cartridge at a point spaced upwardly ,fromthe lower end thereof is an arm I, which includes a rearwardly extendedportion I and a downwardly extended portion 8 provided at its oppositesides with car portions 9. The rearwardly extended portion l and thedownwardly extended portion 8 of the arm are preferably, though notnecessarily, of substantially U-shaped cross-sectiomas shown in Fig. 2,and said arm I includes a collar portion It which fix edly embraces thetube I of the cartridge.

Pivotally connected to the arm I is a hinge element I I, said pivotalconnection between the arm and the hinge element being accomplishedthrough the use of a pivot pin I2 which is extended transversely of thearm and the hinge element through apertures in the ear portions 9 of thearm and in portions I3 of the hinge element which are disposed betweensaid ear portions (see Fig. 2). The hinge element I I comprises spacedapart side portions I I which are integrally connected by web portionsII to provide a unitary structure, and also said hinge element includesan in- 7 tegrally formed, substantially circular plate porment I I areprovided also with hook portions I6 10 located above the hook portionsI5, which are adapted to be engaged by an insulated switch stick when itis desired to detach the assembly comprised of the cartridge and thehinge element II from the switch mounting.

Fixedly supported by the plate portion I 4 of the hinge element I I is athermal unit H, which includes a tubular member I8 (Figs. 4 and 5). Thetubularelement I8 extends upwardly from the plate portion I4, as shownmost clearly in Figs. 20

a and 5, and said tubular elementis surrounded in spaced relationrelative thereto by a casing I9 of suitable insulating material. In theparticular embodiment of the invention illustrated in the drawings, thecasing I9 is circular in hori- 3| zontal section and is seated at itslower end in an annular recess 20 formed in the plate portion II at theouter edge thereof. At the top of the casing I9 the thermal unit Illincludes a cap 2! which includes an upstanding, hollow portion 22 and anannular flange portion 23, the lower face of said flange portion beingin contact with the top edge of the casing l9, and said flange portionbeing provided with an annular, downwardly extended portion 24 whichembraces the upper portion of the casing, as shown in Figs. 4 and 5, soas to maintain the casing in its proper position relative to the cap 2|.

1 At the upper end of the tubular member I8 a head 25 is provided whichis recessed at its outer edge, as indicated at 26. The upper wall of therecess 26 is seated in contact with the top edge of the tubular memberl8, and the lower portion of the head within the recess 26 is extendeddownwardly into the upper portion of the tubular memher a. shortdistance. .Arranged immediately beneath the head 25 is a rod 27 which isfixedly seated at its opposite ends in alined apertures formed in thewall of the tubular member I8 and extends transversely through thehollow interior of the tubular member. The rod 27 has arranged incontact with its lower surface portion a more or less "I'- shapedelement 28 which is provided with a depression or seat 28', the face ofwhich contacts with the lower face of the rod. The upper, substantiallyhorizontal portion of the T-shaped element 28 is provided with a pair ofscrew-threaded openings formed therethrough, through which adjustingscrews 29 are extended, these adjusting screws passing also throughalined apertures formed through the head 25. To the downwardly extendedleg of the T-shaped element 28 a thermo-tripping element 30 is fixedlyattached by means of suitable fastening means 30', said thermo-trippingelement being provided at its lower .1

end with a more or less hook-shaped portion 3|. The cap 2| at the upperend of the thermal unit I I is secured to the head25 located at the topof tubular member I8 by a screw 32, which is extended through an openingformed through the top wall of the cap and is screwed into ascrewthreaded opening formed in the head.

Pivotally attached-to spaced apart extensions 33 of the hinge element II (see Figs. 4 and 6) is a member 34 which includes a body portion 35through which a'pivotpin 3G is extended, said pivot pin being extendedalso through apertures formed through said spaced extensions 33. Themember 34 includes a shaft 31 which is extended outwardly from the bodyportion 35, and this shaft rotatably supports a circumferentiallygrooved pulley 31' formed of insulating material about which, as willpresently appear, the fuse element of the fuse switch passes. Extendedupwardly and rearwardly from the body portion 35 of the member 34 is anextension 38, which is l provided at its free end with a nose portion 39having a' flat underface 39', this flat face being adapted to be engagedby a flat face 40 at the outer end of the hook-shaped portion 3| of thethermo-tripping element 30 as shown most clearly in Fig. 4. I

Arranged to surround the tubular member I8 of the thermal unit I1 is anelongated sleeve 4! formed of material characterized by the ability toact as a heat insulator as well as an electrical insulator. The sleeve4| insulates from the tubular member I8 an electric heating coil 42,this heating coil being interposed between the sleeve 4| and the casingl9, whichfas already stated herein, is formed of suitable electrical insulating material, fiber, for instance. One end of the wire whichproduces the heating coil 42 is attached, as shown most clearly in Fig.2, to a connector 43 by means of a suitable fastening device 44, and theopposite end of said coilproducing wire is attached directly to the webportion li of thehinge element H by means of a suitable fastening device45, as shown in Fig. 4. The connector 43 includes an outstanding,screw-threaded shank 46 (Figs. 1, 2, 3, and 7) at the base of which adisk 41 is located, and mounted on this shank is a wing-nut 48 which hasa washer 49 associated with-it. As is shown most clearly in Fig. 2, thefuse element 5 is electrically connected to the connector 43 by having aportion thereof turned about the shank portion 46 and clamped betweenthe washer 49 and the disk 41.

When the cartridge is disposed in the fusin position, the fuse element 5is held under constant tension, this by reason of the tendency of thehinge element II to turn about the pivot l2 resulting from forces set upby downward pressure exerted against the cartridge by the resilientupper contact E. When the fuse element becomes ruptured upon thecommence of a short circuit, the hinge element l I, freed at its outeror fuse element engaging end and acting under the forces impartedthereto, turns rapidly about the two axes defined by the hinge members Hand the pivot l2. Movement of the hinge element ll about the hingemember H is accompanied by endwise lowering of the cartridge tube,which,

when clear of the upper contact E, swings under action of gravityoutwardly and downwardly to the full open position. It will appear thatthe hinge element I I considered as a lever has a high velocity ratioand that its outer or fuse element engaging end moves very rapidly.Accordingly the ruptured ends'of the fuse element become element 30frees the nose portion of the extension 38 of the member 34, therebypermitting the tensioned fuse element to move said member 34 about itspivot 36, the extension 38 swinging rearwardly and downwardlybeneath'the rearwardly displaced lower end of the thermo-trippingelement and the pulley 31 moving with said extension to a tipped upposition, where the fuse element may slip from the circumferentialgroove of said pulley, as shown by dotted lines in Fig. '7. This freesthe fuse element engaging end of the hinge element I I and permits saidhinge element to turn rapidly about the two axes defined by the hingemembers H and the pivot l2 so as to cause the cartridge to drop out ofthe fusing position, as already explained.

As heretofore explained-herein, the temperature'of the thermo-trippingelement 30 is caused to lag behind the current flow in the heatingelement, so as to care for all temporary load demands withoutinterrupting the circuit. This is accomplished by the use of theinsulating sleeve 4| which is interposed between the thermo-trippingelement and the heating coil 42. Therefore the heat produced by theheating coil, because of ordinary load demands on the circuit, is notsufficient to heat the thermo-tripping element to the tripping pointbecause of the presence of the insulating sleeve. However, if anoverloadbecomes permanent the temperature of the thermotripping elementrises to the point where the thermo-tripping element is actuated and thecartridge immediately drops out of the fusing position, as described.

It is important to note that the thermo-tripping element 30 may beadjusted by manipulating the screws 29 so as to move the T-shapedelement 28 in a rocking or pivotal manner relative to the rod 21. Thusthe lower hook-shaped end of said thermo-tripping element may be po-'sitioned with respect to the nose portion 39 of ducing means forreleasing said cartridge for displacement from'the fusing position byapplying heat to said element of said cartridge-maintaining means. i

2. A fuse switch comprising a switch mounting, a fuse cartridge adaptedto be. releasably supported by the switch mounting, means including athermo-tripping element for maintaining said fuse cartridge in thefusing position, and means for releasing said cartridge for displacementfrom the fusing position, the last-mentioned means including anelectrical heating element adapted to influence said .thermo-trippingelement.

3. A fuse switch comprising a switch mounting, a fuse cartridge adaptedto be releasably supported by the switch mounting, a fuse eley from .thefusing position,

means for releasing said cartridge for displacement from the fusingposition, said means including an electrical heating element arranged inseries with said fuse element and adapted to impart heat to saidtheme-tripping element.

4. A fuse switch comprising a switch mounting, a fuse cartridge adaptedto be releasably supported by the switch mounting, a fuse elementassociated with said fuse-cartridge, means including a thermo-trippingelement for maintaining said cartridge in the fusing position, means forreleasing said cartridge for displacement said means including anelectrical heating element arranged in series with said fuse element andadapted to impart heat to said theme-tripping element, and means forcontrolling passage of heat from said heating element to saidthermo-tripping element.

5. A fuse switch comprising a switch mounting, a fuse cartridge adaptedto be releasably supported by the switch mounting, a fuse elementassociated with said fuse cartridge, means including a thermo-trippingelement for maintaining said cartridge in the fusing position, means forreleasing said cartridge for displacement from the fusing position, saidmeans including an electrical heating element arranged in series withsaid fuse element and adapted to impart heat to said thermo-trippingelement, and insulating means for controlling passage of heat from saidheating element to said thermo-tripping element.

6. ,A fuse switchcomprising a switch mounting, a fuse cartridge adaptedto be releasably supported by the switch mounting in the fusingposition, a hinge element movably connected to said switch mounting andto said fuse cartridge and movable to release the fuse cartridge fordisplacement from the fusing position, heat-responsive means formaintaining said hinge element in position where the fuse cartridge isin the fusing position, and electrical heating means for causing saidheat-responsive means to release said hinge element and permit the fusecartridge to be displaced from the fusing position.

7. A fuse switch comprising a switch mounting, a fuse cartridge adaptedto be releasably supported by the switch mounting in the fusingposition, a hinge element pivotally connected to said switch mountingand to said fuse cartridge and movable to release the fuse cartridge fordisplacement from the fusing position, heat-responsive means formaintaining said hinge element in position where the fuse cartridge isin the fusing position, and electrical heating means for causing saidheat-responsive means to release said hinge element and permit the fusecartridge to be displaced from the fusing position.

8. A fuse switch comprising a switch mounting, a fuse cartridge adaptedto be releasably supported by the switch mounting in the fusingposition, a hinge element pivotallyconnected to said switch mounting andto said fuse cartridge and movable to release the fuse cartridge fordisplacement from the fusing position, heat-responsive means comprisinga thermo-tripping element for maintaining said hinge element in positionwhere the fuse cartridge is in the fusing position, and electricalheating means for causing said heatresponsive means to release saidhinge element and permit the fuse cartridge to be displaced from thefusing position.

enemas movable to release the fuse cartridge for displace-- ment fromthe fusing position, heat-responsive means comprising a thermo-trippingelement for maintaining said hinge element in position where the fusecartridge is in the fusing position, and

electrical heating means for causing said heatresponsive means torelease. said hinge element and permit the fuse cartridge to bedisplaced from the fusing p sition, said thermo-trlpping element andsaid electrical heating means being carried by said hinge element.

10. A fuse switch comprising a switch mounting, a fuse cartridge adaptedto be releasably supported by the switch mounting in the fusingposition, a fuse element associated with said fuse cartridge, a hingeelement pivotally connected to said switch mounting and to said fusecartridge and movable to release the fuse cartridge for displacementfrom the fusing position, said hinge element being engaged by said fuseelement, heat-responsive means for maintaining said hinge element inposition where the fuse cartridge is in the fusing position, andelectrical heating means for causing said heat-responsive means torelease said hinge element from said fuse element and permit the fusecartridge to be displaced from the fusing position.

11. A fuse switch comprising a switch mounting, a fuse cartridge adaptedto be releasably supported by the switch mounting in the fusingposition, a fuse element associated with said fuse cartridge, 'a hingeelement pivotally connected to said switch mounting and to said fusecartridge and movable to release the fuse cartridge for displacementfrom the fusing position, said hinge element being engaged by said fuseelement, heatresponsive means for maintaining said hinge element inposition where the fuse cartridge is in the fusing position, andelectrical heating means arranged in series with said fuse element forcausing said heat-responsive means to release said hinge element fromsaid fuse element and permit the fuse cartridge to be displaced fromthe'fusing position.

12. A fuse switch comprising a switch mounting, a fuse cartridge adaptedto be releasably supported by the switch mounting in a fusing position,a fuse element associated with said fuse cartridge, a hinge elementpivotally connected to said switch mounting and to said fuse cartridgeand movable to release the fuse cartridge for displacement from thefusing position, movable means carried by said hinge means and engagedby said fuse element, heat-responsive means for engaging'said movablemeans and maintaining said hinge element in position where the fusecartridge is in the fusing position, and electrical heating means forcausing said heat-responsive means to release said movable means formovement so as to permit the fuse element to be disengaged therefrom andpermit the hinge element to move to displace the fuse cartridge from thefusing position.

13. A fuse cartridge provided with a fuse element and adapted to bereleasably supported by a switch mounting, movable means associated withsaid fuse cartridge and engaged by the fuse ele ment thereof andoperable to release the fuse cartridge from the fusing position,restraining means oatmeal lot aeitl movable Zoe movement oi eaielmovable rneane, anti electrical heating means arranged to influence Enidrestraining means in a manner to release mov able means for movement.

14. A fuse cartridge provided with inee element and adapted to bereieeeablv supported my a switch mounting, movable means eeeociateti ittn said iuse cartridge anal engaged by the fuse element thereof antioperable to release the time cartridge from the fusing position,restzcaining means carried Toy eairl movable means for restrainingmovement oi said movable means, and electrical heating means cerrleti bysaid movable means and arranged to influence eaiei restraining means ina manner to release said. niovaioie means tor movement.

15. A time eartrltlee provided a lane element and adapted to bereleasaloiv snpnortetl "my a switch mounting, movalole means aeeooiatezlwith said Knee cartridge and eneaeerl by the fuse element thereof andoperable to release the iuee cartridge from the fusing position,reetrainin g means comprising a thermo-ti'll i ing element earrieel bysaid movable means for restraining move ment of saici movable means,anti eleetrieal heating means arrangexi to influence sale means in a erto release movable meane lot movement,

iii. A Knee eai'tnolge provided ele ment anti adenteol ,to be ieleaeablvsupported lay a switch mounting, movable meane aesoeiatezl with eaieliuee oartrirlge and engaged by the time element thereof and operable torelease the time eartridge from the fusing position, resting mecomprising a merino-tripping element carried by said movable means forrestraining movement of said movable means, electrical heating meantaeinngeti to influence said restraining means in a manner to releasesaiol movable means for-move ment, and means for manually adjusting theposition of saicl theme-tripping element.

17. A fuee cartridge proviclezl with a ins e element and adapted to beieleasalolv supported in? a ewitcii mounting, movable means associatedwith said fuse cartridge and engaged in? the i'uee ele ment therecri andoperable to release the fuse cartrlolge from the fusing position,restraining mean-a comprising a thermo-tripping element oat'rietl layeaiel movable means for rwtrainine movement oi said movable means,electrical heating means ar ranged to influence saiel restraining meansin a manner to release said movable means ifot move ment, and meansincline adjusting screws tor manually adjusting the position of saidthen-motripning element.

annt WK.

